21531201355 has 4 divisors (see below), whose sum is σ = 25837441632. Its totient is φ = 17224961080.

The previous prime is 21531201353. The next prime is 21531201361. The reversal of 21531201355 is 55310213512.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21531201355 - 2¹ = 21531201353 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21531201353) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2153120131 + ... + 2153120140.

It is an arithmetic number, because the mean of its divisors is an integer number (6459360408).

Almost surely, 2^21531201355 is an apocalyptic number.

21531201355 is a deficient number, since it is larger than the sum of its proper divisors (4306240277).

21531201355 is an equidigital number, since it uses as much as digits as its factorization.

21531201355 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4306240276.

The product of its (nonzero) digits is 4500, while the sum is 28.

Adding to 21531201355 its reverse (55310213512), we get a palindrome (76841414867).

The spelling of 21531201355 in words is "twenty-one billion, five hundred thirty-one million, two hundred one thousand, three hundred fifty-five".